In known coils and transformers, such as dry-type transformers, two or more coils can be arranged axially one above the other on a core limb, wherein each coil has an inner winding, or low-voltage winding, and an outer winding, or high-voltage winding. The spacing between two coils which is specified for a sufficient dielectric strength is calculated depending on the connection of the coils. In addition, it is usual for barriers to be arranged between the inner winding and the outer winding of a coil, which barriers are intended to prevent an electrical flashover between the two windings.
FIG. 4 shows a lateral section of an arrangement including at least two coils in accordance with a known implementation. As shown in FIG. 4, a core limb includes a first coil 1 and a second coil 4 are arranged axially one above the other. The first coil 1 has two windings 2, 3 arranged radially one above the other, wherein winding 2 is also designated as inner winding or low-voltage winding, and winding 3 is also designated as outer winding or high-voltage winding. The second coil 4 has two windings 5, 6 arranged radially one above the other, wherein winding 5 is also designated as inner winding or low-voltage winding, and winding 6 is also designated as outer winding or high-voltage winding.
A plurality of barriers 51 is arranged between the inner winding 2 and the outer winding 3 of the first coil 1 in order to reliably prevent an electrical flashover between the two windings 2, 3. In a similar manner, a plurality of barriers 52 is arranged between the inner winding 5 and the outer winding 6 of the second coil 4 in order to reliably prevent an electrical flashover between the windings 5, 6.
The axial spacing between the two coils 1, 4, to be determined in dependence on the connection of the coils and the voltage differences, is designated as A1 (measured between the inner windings 2, 5). The barrier projection, that is to say the amount by which a barrier projects over the end face of a winding, arranged perpendicular to the winding axis W, is designated as B (measured between winding 3 and barrier 51 and between winding 6 and barrier 52).
For higher voltages or voltage differences, the specified barrier projections over the windings of the individual coils can be relatively large and therefore lead to a lengthening of the core limb—e.g., core limb length L1.